Computed radiography (CR) is based on the use of photostimulable phosphors, also known as storage phosphors. In CR imaging plates that utilize storage phosphors, a useful image is not derived from light emitted in prompt response to incident X-ray radiation, but rather from subsequent emission when the latent image, consisting of trapped charge, is optically stimulated (e.g., using laser light) and released from metastable traps. This triggers a process called photostimulated luminescence (“PSL”) resulting in the emission of light of a shorter wavelength than the laser light in an amount that is proportional to the original absorbed X-ray irradiation.
For powder based storage phosphor CR imaging plates, a “doctor blade” technique may be used to spread a binder loaded with a storage phosphor onto a substrate to form a continuous uniform layer. Photostimulation laser light scattering in the phosphor during readout and photostimulated light scattering before exiting the storage phosphor layer may result in poor image quality. Alternatively, vapor deposition may be used to grow needle like structures of phosphor. However, growing needle like structures by vapor deposition is slow, expensive, and potentially size limited.
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